Problem

What is a DNSBL?

Solution

Spam and Open Relay Blocking System, also known as SORBS is a service provided by Proofpoint Inc. (prior to acquisition in July 2011 was GFI software)  SORBS is another DNSBL service provider which effectively blocks emails from more than 12 million host servers known to disseminate spam, phishing attacks and other forms of malicious email.

History of SORBS

The Spam and Open Relay Blocking System (SORBS) was originally conceived in 2001 as an anti-spam project where a servers would check in real-time all received email to determine if that email was sent via various types of proxy and open-relay servers.